Neck Muscle Inhibition Induced by Intra-oral Stimulation in Humans

Several studies have been made on trigemino-cervical reflexes. Objective: To evaluate the effect of the intraoral stimulation on the neck muscle activities. Methods: The experiments were performed on 7 healthy volunteers (F=4; M=3; mean age=24.6yrs). Electrical stimuli (0.2ms duration, 0.3Hz) were applied to the maxillary attached gingiva at intensities of 1-13 x perceptive threshold. Surface EMG activities were obtained from the ipsilateral dorsal neck muscles before and after local anesthesia to the periodontal tissues by means of fine wire electrodes. The EMG responses were full-wave rectified, and then averaged from 20 ms before the stimulus to 180 ms afterward. Results: The integrated value between 40-50 ms after the stimulation (P40-50) was significantly reduced than that of pre-stimulus before anesthesia (P=0.028, Wilcoxon test). No significant differences were found in P40-50 after anesthesia (P>0.9, Wilcoxon test). Conclusion: These results suggest that the afferent information from the intraoral receptors influences the dorsal neck muscle activities.